Structural and Electronic Effects of Carbon‐Supported PtxPd1−x Nanoparticles on the Electrocatalytic Activity of the Oxygen‐Reduction Reaction and on Methanol Tolerance |
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Authors: | Dr. Shih‐Hong Chang Dr. Wei‐Nien Su Dr. Min‐Hsin Yeh Dr. Chun‐Jern Pan Dr. Kuan‐Li Yu Din‐Goa Liu Dr. Jyh‐Fu Lee Prof. Bing‐Joe Hwang |
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Affiliation: | 1. Department of Chemical Engineering, National Taiwan University of Science and Technology, #43, Sec.4, Keelung Rd., Taipei, 10607, Taiwan (R.O.C.);2. National Synchrotron Radiation Research Center, 101 Hsin‐Ann Road, Hsinchu Science Park, Hsinchu 30076, Taiwan (R.O.C.) |
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Abstract: | We report a systematic investigation on the structural and electronic effects of carbon‐supported PtxPd1?x bimetallic nanoparticles on the oxygen reduction reaction (ORR) and methanol oxidation reaction (MOR) in acid electrolyte. PtxPd1?x/C nanocatalysts with various Pt/Pd atomic ratios (x=0.25, 0.5, and 0.75) were synthesized by using a borohydride‐reduction method. Rotating‐disk electrode measurements revealed that the Pt3Pd1/C nanocatalyst has a synergistic effect on the ORR, showing 50 % enhancement, and an antagonistic effect on the MOR, showing 90 % reduction, relative to JM 20 Pt/C on a mass basis. The extent of alloying and Pt d‐band vacancies of the PtxPd1?x/C nanocatalysts were explored by extended X‐ray absorption fine‐structure spectroscopy (EXAFS) and X‐ray absorption near‐edge structure spectroscopy (XANES). The structure–activity relationship indicates that ORR activity and methanol tolerance of the nanocatalysts strongly depend on their extent of alloying and d‐band vacancies. The optimal composition for enhanced ORR activity is Pt3Pd1/C, with high extent of alloying and low Pt d‐band vacancies, owing to favorable O? O scission and inhibited formation of oxygenated intermediates. MOR activity also shows structure dependence. For example, Pt1Pd3/C with Ptrich?corePdrich?shell structure possesses lower MOR activity than the Pt3Pd1/C nanocatalyst with random alloy structure. Herein, extent of alloying and d‐band vacancies reveal new insights into the synergistic and antagonistic effects of the PtxPd1?x/C nanocatalysts on surface reactivity. |
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Keywords: | fuel cells nanoparticles oxygen reduction reaction palladium platinum |
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